In America, a considerable quantity of paper is annually made from pulp prepared from cane (Arundinaria macrosperba). It grows profusely in the lowlands of the Mississippi, and along the rivers of N. and S. Carolina, and, labour being cheap in those districts, it can be very economically gathered. The fibre, which is sold to the paper-maker in the form of half-stuff is obtained by a very curious process. The cane, cut into pieces, is tightly packed into strong cast-iron cylinders, called "guns," about 22 ft. long and 1 ft. in diameter, fitted with strong ends, and provided with a very strong dome for containing steam. Steam is sent into these cylinders until a pressure of about 180 lb. a sq. in. is indicated ; this is kept up for about 15 minutes ; the end of the cylinder is then suddenly opened, and the whole mass of cane is forced violently out against a target pro vided in case of accident. While in the gun, the pores of the cane are filled with the highly compressed steam, which, on reaching the outer air, expands rapidly, with a loud report, like that of a cannon, with the effect of thoroughly disintegrating the cane, and reducing it to a fibrous state. It appears that the effect is due partly to chemical and partly to mechanical action. The fibre thus produced is well washed, and beaten under revolving rolls fitted with knives, similar to those used in the beating-engines of paper-mills.
Waste paper.—A very important source of material is waste paper, large quantities of which are remanufactured. Any kind of old paper can thus be utilized, and as it has already undergone the necessary treatment, very little more is required to prepare it. It generally goes by the names of " broke" or " imperfections." MANUFACTURE.—Treatment of Esparto.—As by far the largest proportion of the paper manufac tured in Great Britain is made, if not entirely, at least largely, of esparto, and as the processes to which this fibre is subjected are typical of the treatment which other fibres undergo, with such exceptions as will be pointed out in their proper place, the methods in general use for the prepara tion of this important material will fitly occupy the foremost place.
The first process is the removal of accidental impurities, such as pieces of weed, root-ends, Sze, which, from their nature, are with great difficulty boiled and bleached, and would not only there fore tend to deepen the colour of the bulk of fibre produced, but would be liable to appear subse quently in the finished paper as dark-coloured specks, technically known as " sheave." This treatment, which is called "dry-picking," in contradistinction to a subsequent process, known as " wet-picking," is generally performed by girls, who work at separate tables placed in a long row. A portion of the table set apart to each girl is covered with a very coarse iron-wire gauze, on which small bunches at a time of esparto are spread, to enable the worker more readily to see the imperfections, and through which small impurities, such as sand, pass away. It has been proposed
to economize time and labour by using a machine for the purpose of dry-picking. One of the best machines of the kind is that made by Masson and Scott. In it, the grass is first put through a conical willow, where all the dust is removed by a blast, and carried away into a separate chamber. The grass so purified is brought forward on an endless travelling felt, at each side of which, girls are placed to remove the roots and other objectionable bodies. The grass so sorted is then taken to the boiler-house.
Boiling.—There are several sorts of boilers in use, but only two call for special notice. The one in ordinary use is shown in Fig. 1049. The grass is put in by the door E, which can be firmly fastened down by the screws F. The steam enters by the pipe A, which goes a little below the perforated bottom B. Surrounding the steam-pipe is a wider pipe C, open at the top, and made slightly trumpet-shaped, also open at the bottom, below the false bottom. It carries at its lower end a kind of shoulder, on which the false bottom rests. The enlarged part of this tube beyond the shoulder has two or more openings G, through which the liquor can freely pass. The action of the boiler is as follows :—The steam from the pipe A heats the liquor that has drained from the grass through the perforations in the false bottom B, and, forcing it up the wide pipe C, causes it to strike against the dome or bonnet D, and distribute itself again over the grass. This is tech nically called " vomiting." The boiler is emptied by the door H, and the liquor is run off by the tap I. The boilers aro usually supplied with a safety-valve K. The weights L are for convenience in lifting the door E. While the boiler is being filled with grass, the vomit is usually kept going ; this has the effect of softening the grass, and allowing it to be more closely packed.
This form of boiler is not suitable for use with very high-pressure steam. Under such circum stances, it is slightly modified. In Sinclair's patent high-pressure boiler, there are two false bottoms communicating with each other by means of short pipes. The vomit-pipe extends as far as the lower partition, and the steam enters at the bottom of the boiler. In Roeckner's, the compartment formed by the perforated bottom communicates with the top of the boiler by means of a pipe outside, which has a bend in it, forming a complete circle. This is with the object of keeping the pipe always full of liquor. The vomit is produced by steam entering the pipe at the bottom of the bend. In some mills, rotary boilers are employed for esparto, but their use is far from being general.